Grinding machine

ABSTRACT

This invention relates to a grinding machine and, more particularly, to apparatus for forming a surface of revolution by the abrasive process, wherein the force between the wheel and workpiece is closely controlled.

United States Patent 1191 [111 3,717,960 Kuniholm 1451 Feb. 27, 1973 [54] GRINDING MACHINE [56] References Cited [75] Inventor: glitz-gin L. Kuniholm, Worcester, UNITED STATES PATENTS 2,083,748 6/1937 Steiner ..s1/16s.9x [73] Asslgnee' g' ig fig g companywor 2,486,244 10/1949 Balsigeretal. ....5l/l65.92X

3,052,069 9/1962 Grzymek ..5l/l65.9

[22] Filed: June 28, 1971 3,056,239 10/l962 Seidel et al. ..51/l65 R [21] Appl.No.: 157,693

Related U.S. Application Data Continuation of Ser. No. 896,900, Aug. 1, 1969, abandoned.

Primary Examiner-Harold D. Whitehead Attorney-Norman S. Blodgett [57] ABSTRACT This invention relates to a grinding machine and, more between the wheel and workpiece is closely controlled.

2 Claims, 3 Drawing Figures FORCE (LBS) PATENTED FEB271975 FIG. 2

FINAL INVENTOR. SIZE MARTIN 1.. KUNIHOLM TIME (SEQ) ATTORNEY GRINDING MACHINE This application is a continuation of application Ser. No. 846,900, filed Aug. 1, l969 and now abandoned.

BACKGROUND OF THE INVENTION In the generation of surfaces by grinding there are many advantages to be gained by using high forces for the primary removal of material from the workpiece. However, it has also been discovered that the best surface finish is produced at a force level that is considerably below the high force which gives the fastest stock removal. In changing from one force to the other, however, it has been found that the rapid release of force causes a vibratory situation that results in poor finish. On the other hand, a slow change of forces can cause a time-consuming surface-finishing operation that ties the grinding machine up in an uneconomical manner. Also, performing the surface-finishing operation by the spark-out method (wherein the grinding force is determined by the spindle deflection which is gradually reduced) is also time consuming. With a worn wheel the force may drop to a level such that cutting ceases and the desired size is never attained. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a grinding machine in which the force between the wheel and the workpiece is regulated in a predetermined pattern.

Another object of this invention is the provision of a grinding machine making use of a cycle which will give the most rapid stock removal while producing a good surface finish.

A further object of the present invention is the provision of a grinding machine in which stock removal and surface finish take place in a minimum period of time.

It is another object of the instant invention to provide a grinding machine in which a high quality of surface finish is produced irrespective of whether the wheel is new or old and without consuming a long period of time when the wheel becomes worn.

SUMMARY OF THE INVENTION In general, the invention consists of a base on which are mounted a workpiece support and a wheel support, there being a feed mechanism to bring about relative movement between the two supports to cause grinding engagement between the wheel and the workpiece. A first control means causes the engagement to take place at a predetermined force pattern during grinding. A second control means causes the engagement to take place at a predetermined force decay pattern from the end of the first grinding to a final size point.

More specifically, the second control means consists of a stop member associated with the base and a spring element associated with the wheel support, the deflection of the spring element by the pressure of the stop member absorbing successively increasing amounts of the force to decrease the force between the wheel and the workpiece. A gage in the form of an air nozzle is associated with the spring element andis operative to terminate the grinding operation when a predetermined deflection of the spring element has taken place.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

FIG. 1 is a plan view with portions broken away of a grinding machine embodying the principles of the present invention,

FIG. 2 is a sectional view taken on the line IIII of FIG. 1, and

FIG. 3 is a graphic representation of a grinding cycle produced by the machine.

Referring first to FIG. 1, wherein are best shown the general features of the invention, the grinding machine, indicated generally by the reference numeral 10, is shown as consisting of a base 11 having ,a flat horizontal upper surface on which are mounted a workhead I2 and a wheelhead 13. The workhead is carried on a workhead table 14 which is mounted for longitudinal motion on the base 11 by means of ways 15. Similarly,

' the wheelhead 13 is carried on a wheelhead table 16 which is mounted for transverse sliding motion on the base 11 by means of ways 17. Extending between the wheelhead table 16 and the base 11 is a feed cylinder 18 which is suitably provided wit fluid pressure to bring about movement of the table 16 transversely of the base. Similarly, a hydraulic cylinder 19 connects the table 14 to thebase 11 and brings about longitudinal movement of the table 14 over the ways 15.

Extending from the wheelhead 13 is a rotatable spindle 21 carrying on its outer end an abrasive wheel 22. Carried by the workhead 12 and rotated thereby is a workpiece 23; for the purpose of illustration, this workpiece is shown as the race of a ball bearing. The inner bore is being ground by the abrasive wheel 22 and the workpiece is supported on its outer cylindrical surface. Residing in the bore of the workpiece during the grinding operation is a pneumatic air gage 24 of the wellknown type which gage is connected to a control box 25. The control box 25 provides a flow of air to the gage 24 in a well-known manner; the amount of air that is able to pass between the surface of the gage and the surface of the bore of the workpiece is an indication of the workpiece size and this flow is transmitted to the control box 25 which contains various pressure switches to operate electrically to open and close solenoid valves in the hydraulic circuitry of the machine.

Slidable on the upper surface of the base 11 is a block 26 which, at its rearward end, is threadedly attached to a threaded shaft 27 which, in turn, is driven by a motor 28 fastened to the base 11. This motor is of the type capable of small discreet rotary increments in response to pulses received from an electrical control. By regulating the nature and number of the pulses from the electrical control it is possible to rotate the motor quickly or slowly in exact amounts to make the block 26 move transversely over the surface of the base 11. In the present apparatus, this motor is used to produce compensation after dress and to provide for retraction of the wheel at a suitable time of the grinding cycle, as is well known. A dressing diamond 29 is mounted on the workhead table 14 in position to engage the wheel 22 during a dressing traverse at a suitable time in the grinding cycle.

The block 26 is provided with a transverse slot 31 and in this slot resides a horn 32 extending downwardly from the undersurface of the wheelhead table 16. The front of the block 26 is provided with a hardened metal insert 33. Mounted on the front portion of the wheelhead table 16 is an adjustable stop 34 having a contact rod 35 extending toward the block 26 and toward the metal insert 33. Mounted at the front of the stop is an adjusting knob 37.

Extending downwardly from the table 16 is a spring element such as a thin-walled apron 36. In the preferred embodiment this is a separate piece of metal which is bolted at its upper edge to an undersurface of the table; the bottom and side edges, however, are free, so that the apron 36 acts as a cantilevered spring. The central portion of the apron is provided with an integral knob 38 through which the stop 34 is threaded. Also bolted on the underside of the table 16 is a support 39 having an opening 41 surrounding the stop 34 so that that support and stop never touch. Mounted on the lower end of the support is a gage 42 of the pneumatic type having a nozzle 43 close to and directed toward the flat rear surface 44 of the apron 36. Extending from the gage is a conduit 45 which is connected to the control box 25 so as to operate a FINAL SIZE switch and to terminate the grinding cycle.

The operation of the grinding machine will be best understood by reference to the grinding cycle diagram in FIG. 3, wherein the abscissa represents the passage of time an the ordinate represents the force between the abrasive wheel 22 and the workpiece 23. At the beginning of the cycle, the wheel 22 is introduced into the bore in the workpiece by the operation of the cylinder 19; longitudinal reciprocation takes place in the well-known manner. The cylinder 18 is actuated to bring about transverse feed of the wheel toward the surface of the workpiece to be finished. The engagement of the wheel and workpiece builds up the force very quickly to a high level commensurate with a ROUGH GRIND. The build-up of this force is attended by deflection of the spindle 21. As soon as the gage 24 indicates to the main control 25 that a predetermined bore size has been reached, the wheel is retracted for a dressing operation in conjunction with the diamond 29. After dressing has been completed, the wheel is again advanced toward the workpiece and the force is built up to a second level (somewhat lower than that used in ROUGH GRIND) for a FINISH GRIND. As the FINISH GRIND progresses, the wheelhead table 16 advances transversely across the base and also relative to the block 26. The movement of the table 16 causes the rod 35 of the stop 34 to approach the insert 33 on the block and, eventually, to contact it. Further advancement of the table in this way causes the stop to bend the apron 36 in the manner of a spring.

Now the grinding force during the FINISH GRIND was determined by the pressure of the fluid in the crossfeed cylinder 18. At that time the only resistance to the transverse movement of the table 16 was the spring action of the spindle 21 deflected by the engagement of the wheel 22 with the workpiece 23. In other words, the grinding force absorbed the entire force produced by the cylinder 18. Once the stop 34 contacts the block 26 at the point A, however, the total force from the cylinder is divided between (l) the deflection of the spindle, and (2) the deflection of the apron 36. This causes a decrease in the grinding force from the point A to a FINAL SIZE point B. This last point is determined by the gage 42 as the surface 44 of the apron 36 moves further and further from the nozzle 43. The fact that FINAL SIZE has been reached is communicated through the conduit 45 to the main control box 25 and the grinding cycle is terminated.

The apron 36 is constructed as a spring element that operates according to Hookes law, but it should be understood that various types of spring elements can be selected with various stress-strain characteristics to produce various shapes to the force curve between the points A and B. In a practical embodiment of the invention, the force along the plateau during FINISH GRIND was brought about with the force in the spindle at 60 psi. When the point A is reached, this quickly drops to 20 psi as is evident from the curve. The panel 36 flexes beyond its captive point, while the spindle deflection and force remain essentially constant at the predetermined force level where the desired surface finish quality is known to be obtained. Therefore, FINAL SIZE is reached in the shortest possible time for the quality of finish being produced.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1. A grinding machine, comprising a. a base on which are mounted a workpiece support adapted to carry a workpiece and a wheel support adapted to carry a wheel,

b. a feed mechanism for bringing about relative movement between the two supports to cause machining engagement between the wheel and the workpiece, comprising c. a hydraulic cylinder to cause the said engagement to take place at a predetermined force pattern during a grind,

d. a control means to cause the said engagement to take place at a predetermined force decay pattern from the end of the said grind to a final size point, the control means'consisting of a stop member associated with the base and a spring element associated with the wheel support, the deflection of the spring element by the pressure of the stop member absorbing successively increasing amounts of the force to decrease the force between the wheel and the workpiece, and

e. a gage associated with the spring element and operative to terminate the grinding operation when a predetermined deflection of the spring element has taken place.

2. A grinding machine as recited in claim 1, wherein the spring element is a flexible panel and the gage is an air nozzle located to direct air flow toward a surface of the panel. 

1. A grinding machine, comprising a. a base on which are mounted a workpiece support adapted to carry a workpiece and a wheel support adapted to carry a wheel, b. a feed mechanism for bringing about relative movement between the two supports to cause machining engagement between the wheel and the workpiece, comprising c. a hydraulic cylinder to cause the said engagement to take place at a predetermined force pattern during a grind, d. a control means to cause the said engagement to take place at a predetermined force decay pattern from the end of the said grind to a final size point, the control means consisting of a stop member associated with the base and a spring element associated with the wheel support, the deflection of the spring element by the pressure of the stop member absorbing successively increasing amounts of the force to decrease the force between the wheel and the workpiece, and e. a gage associated with the spring element and operative to terminate the grinding operation when a predetermined deflection of the spring element has taken place.
 2. A grinding machine as recited in claim 1, wherein the spring element is a flexible panel and the gage is an air nozzle located to direct air flow toward a surface of the panel. 